I think the (not-too-distant) future of home computing will have a lot in common with today's PCs. Articles like this one always seem to underestimate the amount of real creative or productive work people want to do -- something which is still a challenge on the iPads of today. Have YOU compared typing on a small screen to a big one?
With custom manufacturing becoming affordable, as traditional computers start dying, open source hardware will start replacing them. I think we are seeing the first steps in this direction with Raspberry PI, hobbyist open hardware people, 3D printing (in the future: cheap chip printing?), CryogenMod, etc.
They say that, but with all the device consolidation features (iCloud, syncing, unified messages, launchpad, dock with no indicator lights, automatic process management), they are playing out a different tune.
I think Apple is aware of this trend, and is going to eventually act on it.
I still hope Ubuntu does it well first, because I'd love to have an affordable OSS solution.
You might be right that desktops will always outperform portable devices (even though the gap is certainly narrowing), but mobile phones used this way are so convenient that the tradeoff is worth it.